Seal-testing device

ABSTRACT

A device for indicating whether a lip-type seal may be satisfactorily reinstalled. A simulated shaft and seal retaining environment is provided, and the simulated shaft has a plurality of radially extending members normally urged radially outwardly at a predetermined pressure. When the seal urges all of these members in at a somewhat greater pressure, a series circuit is completed to give a signal. The seal is deemed satisfactory if the signal remains in operation for a predetermined time interval.

United States Patent inventors William H. Neuman Cedar Falls, Iowa;

James A. Repella, Madison Heights, Mich. App]. No. 53,333 Filed Jan. 16,1970 Patented May 25, 1971 Assignee Federal-Mogul CorporationSouthfield, Mich.

SEAL-TESTING DEVICE 3 Claims, 3 Drawing Figs.

US. Cl 73/88R,

Int. Cl G0ln 3/08 Field of Search 73/ 1 O0,

120, 37, 37.5, 40, 46, 49.4, 49.8, 88,81, 89; 33/174L, 178e, l78R, 141

[56] References Cited UNITED STATES PATENTS 3,188,855 6/1965 Dega 73/373,286,512 11/1966 Jagger et al. 73/88 3,447,361 6/1969 Schmitt 73/88Primary Examiner-Richard C. Queisser Assistant ExaminerMarvin SmollarAttorney-Owen, Wickersham, Erickson P NIEU was 1971 31580.06 1

SHEET 1 0F 2 47 47a 47b 47 5o (Lani gig? 72 (74 I INVENTORS WlLLI M H. NMAN JXM S A. RE LLA 0cm UM L ATTORNEYS SHEET 2 [IF 2 m n WNE 1 .R A 9 mS LM J m A M Wm. v L H L (N I mm mm Q Q. 3 m; wm mm 9 3 @V V? 1PM NM mmm mm J mm mm v @v N FF? 7 wv mv mm ow .8 mm mm Om (t j avg m NV mmwm @won mm PATENTED "M25 :97:

SEAL-TESTING DEVICE This invention relates to a device for testing theoperability of a shaft seal of the lip type.

The general rule in the shaft seal industry is never to reinstall alip-type of seal, one it has been removed. There are good reasons forthis rule, because the act of removal of most lip-type shaft seals isliable to damage them, and in a large percentage of cases effectivelydestroys their functional capabilities. A particular reinstalled sealmay or may not leak, but a large percentage of reinstalled seals wouldleak, and since lip seals are usually relatively inexpensive both incomparison with the time it takes to install or reinstall them and incomparison with the equipment which the seal protects, reinstallation isgenerally considered risky, and it is economical to put in a new sealwhenever an old seal has to be removed.

However, throwing old seals away and putting in new seals becomesexpensive in some instances where relatively expensive seals are used.An example is a railroad journal box seal for tapered roller bearinginstallations, and there are other expensive lip seals in someinstallations. In such installations, interest has been lately expressedin reconditioning the expensive bearings, and in order to reconditionthe bearings, the seal must be removed. When the bearings have beenreconditioned, the question arises whether the seal can be safelyreinstalled. [f the seal can be safely reinstalled, the savings arequite significant, but if the seal would leak after installation, theexpensive bearings it protects would be damaged and the cost would faroutweigh the cost of the seal. Rather than throw away every one of theserelatively expensive lip seals, the present invention provides a testwhich determines whether the seal can be safely reinstalled, eliminatingboth guess work and waste. When a seal is placed on the proper testapparatus of this invention, it comes into engagement with severalspring-loaded actuating pins; if the seal lip places a satisfactoryradial load upon each pin, each pin closes a switch. The switches are inseries, and if all of them close, a signal is given: e.g., a light goeson. An interval timer also is started to enable the tester to see thatthe light will stay on for a predetermined test interval. The seal isrejected if the light does not come on or if it does not stay lightedduring the entire period of the test interval. If the seal passes thetest, it may safely be reinstalled, subject only to visual inspectionfor tears or obvious serious blemishes.

Other objects and advantages of the invention will appear from thefollowing description of a preferred embodiment.

in the drawings:

FIG. 1 is a top plan view of a seal test unit embodying the principlesof the invention.

FIG. 2 is an enlarged view in elevation and partly in section of theunit of FIG. 1, taken along the line 2-2 in FIG. 1.

FIG. '3 is a diagram of an electrical circuit for the unit.

The seal test unit shown in FIGS. 1 and 2 has exterior surface portionsthat simulate that of the seals normal installed environment.Perpendicular to a flat base 11 is a cylindrical surface 12 which isjoined by a step 13 to an inset cylindrical surface 14. A plurality ofscrews 15 on the step 13 enable precise adjustment of the location of aseal to be tested. The cylindrical surface 14 is connected by anotherstep 16 to a cylindrical surface 17 which corresponds to the shaft (orsimilar surface) which the main lip 21 of the seal 20 is to contact. Thestep 13, with its screws 15, and the surface 14 act to provide seatingfor the seal 20 by simulating the normal retention of the installed seal20, though they may be somewhat different from the corresponding partsin the actual installation, and they assure perfect alignment of theseal 20 with respect to the lip 21 and the surface 17. All thesesurfaces are preferably on a unitary body 18.

Various types and sizes of seals may be tested, and differences in sealscall for differences in the test unit. The seal 20 is used herein onlyas an example of one type of seal that is economically worth testing forpossible replacement. The seal 20 has a main case 22 with a longcylindrical portion 23 followed atone end by an outward step 24 and ashorter cylindrical terminal portion 25. At the other end of thecylindrical portion 22 is a radial flange 26 leading in to a seal anchorportion 27 to which an elastomeric seal element 28 of suitable type issecured. The element 28 provides the main (or oilretaining) lip 21,urged in this instance by a spring 30. Other types of anchorage for theelement 28 to the case 22 may be used, for the precise structure of theseal is not important to the present invention, so long as the rightdimensions obtain on the unit 10. An inner case or guard 31 may be heldby a crimp 32 of the outer case 22, as shown. This structure, again,plays no function in the testing. The seal 20 should, of course, bevisually inspected for obvious defects.

At a plurality of locations, preferably four spaced around the circularperiphery of the unit 10, the invention provides actuator pins 35 whichextend radially through radial openings 36 in the body 18 and extendthrough the surface 17. To each of the pins 35 are secured two adjustingnuts 33 and 34 and a washer 37 that faces a lug 38 on the body 18, and aspring 40 is placed around the stem 39 of the pin 35 between the washer37 and the lug 38 and bears against them. The pin 35 thus is normallyforced outwardly at a predetermined load and resists being forced in.Another pair of adjusting nuts 41 and 42 enables precise location of theouter surface 43 of the pin 35. The inner end 44 of the pin 35 is tappedand into it is threaded a stud 48, on which is threaded a locking nut45. The end 49 of the stud 48 bears against the lever arm 46 of amicroswitch 47 or other suitable type of electrical switch. The idea isthat the pin 35 can close the microswitch 47 only when a predeterminedradial load is placed on the pin 35 by the seal lip 21. If the radialload of the lip 21 is insufficient to close the switch 47, the seal 20is not safe to use, and therefore the test would result in itsrejection, whereas if the seal 20 is safe to reuse, its lip 21 willplace the desired load on the microswitch lever arm 46, and the switch47 will be closed. 7

As shown in FIG. 3, several (e.g., four) microswitches 47, 47a, 47b, and470, are in series between a source 48A of current and a signal 50, suchas light, which may be green or otherwise give some signal. The switches47, 47a, 47b, and 470 and the light 50 are alsoin series with a doublepole, double throw switch 51. The pole 52 of the switch 51 is thrown bya button 53 to a test position against a contact 54 to determine whetherthe light 50 is operative and against a contact 55 during actual testingof the seal. In parallel with the four switches 47 47a, 47b, 47c, and47d, is another light bulb 56 to indicate that the circuit is on.

A timing device 60 is used and is actuated upon the commencement of thetest. The device 60 includes a microammeter 61 wired in series with anadjustable resistance 62 and two fixed resistors 63 and 64. Across theresistors 63 and 64 is a capacitor 65, preferably of the electrolytictype, which is charged by a network 70 of diodes 66, 67, 68, and 69 onlywhen at least one microswitch 47, 47a, 47b, or 47cis open, since one end71 of the network is connected by a lead 72 to the input side of theswitch 47, and the other end 73 of the network is connected by a lead 74to the output side of the microswitch 47c. The two sides 75 and 76 ofthe network 70, are connected respectively to the resistors 63 and 64and are crossed by the capacitor 65. When all of the microswitches 47,47a, 47b, and 47c are closed, the current is shunted around the network70 by what is really a short circuit. Thus the capacitor 65 then beginsto discharge through the resistors 63, 62, and 64 and the meter 61. Theresistor 62 enables adjustment of the RC time constant governingdischarge of the capacitor 65. During discharge, the meter 61 indicatesthat discharge is going on.

Thus, if the light 50 comes on at all, this means that all themicroswitches 47, 47a, 47b, and 470 have been closedby the seal lip 21having exerted the required amount of pressure, and at the same time thetiming device 60 starts a time interval going. At the end of that time,the meter 61 signals the conclusion of the time interval, and if thelight 50 is still on, the test is successful. it is then safe toreinstall the seal 20, but if the seal 20 is not safe to use the light50 will not stay on for the whole interval or will not come on in thefirst place. Usually the test interval is about fifteen seconds, but itmay be adjusted as described to any desired interval.

The invention may also be used as a safety check for new seals.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting We claim:

1. A device for indicating whether a lip-type of shaft seal exerts arequired lip pressure and is safe for installation, including incombination:

a cylindrical shaft-simulating surface having a plurality of radialopenings therethrough,

a test pin in each said opening extending radially toward the center,

pressure means urging each said test pin radially outwardly,

switch means for each said pin actuated only when the pressure exertedradially inwardly thereon is above a predetermined level, as it will bewhen the shaft seal being tested is installed on said shaft-simulatingsurface and is safe for installation, and

signal means actuated only when all said switch means are actuated.

2. The device of claim 1 having timing means actuated upon actuation ofall said switch means and means indicating the conclusion of a timedperiod initiated and closed by said timmg means.

3. The device of claim 1 wherein said timing means comprises an R-Ccircuit having a capacitor that begins discharge when all said switchesare actuated and a current meter indicating flow of current duringdischarge of said capacitor.

1. A device for indicating whether a lip-type of shaft seal exerts arequired lip pressure and is safe for installation, including incombination: a cylindrical shaft-simulating surface having a pluralityof radial openings therethrough, a test pin in each said openingextending radially toward the center, pressure means urging each saidtest pin radially outwardly, switch means for each said pin actuatedonly when the pressure exerted radially inwardly thereon is above apredetermined level, as it will be when the shaft seal being tested isinstalled on said shaft-simulating surface and is safe for installation,and signal means actuated only when all said switch means are actuated.2. The device of claim 1 having timing means actuated upon actuation ofall said switch means and means indicating the conclusion of a timedperiod initiated and closed by said timing means.
 3. The device of claim1 wherein said timing means comprises an R-C circuit having a capacitorthat begins discharge when all said switches are actuated and a currentmeter indicating flow of current during discharge of said capacitor.